Implicit User Profiling in News Recommender Systems Jon Atle Gulla1, Arne Dag Fidjestøl1, Xiaomeng Su2 and Humberto Castejon2 1Dep. of Computer and Information Science, Norwegian University of Science and Technology, Trondheim, Norway 2Telenor Group, Trondheim, Norway Keywords: Recommender Systems, Personalization, User Profiling, Mobile News, Big Data, Information Retrieval. Abstract: User profiling is an important part of content-based and hybrid recommender systems. These profiles model users’ interests and preferences and are used to assess an item’s relevance to a particular user. In the news domain it is difficult to extract explicit signals from the users about their interests, and user profiling depends on in-depth analyses of users’ reading habits. This is a challenging task, as news articles have short life spans, are unstructured, and make use of unclear and rapidly changing terminologies. This paper discusses an approach for constructing detailed user profiles on the basis of detailed observations of users’ interaction with a mobile news app. The profiles address both news categories and news entities, distinguish between long-term interests and running context, and are currently used in a real iOS mobile news recommender system that recommends news from 89 Norwegian newspapers. 1 INTRODUCTION several stories or proper news overviews, and (iii) the lack of an efficient keyboard hampers the With the growing popularity of smartphones and reader’s interaction with the news apps. tablets an abundance of news apps have been However, an efficient recommender system introduced over the last few years as alternatives to needs some understanding of the users’ preferences online web news sites. News aggregator apps like and interests. Some news apps do not keep any News360, Flipboard, Pulse and Feedly are not linked particular information about the user and there is no to one particular media house, but make use of user-tailoring of news or recommendations offered. publically available news stories as soon as they are Other apps allow the user to select a category or post published on the Internet. These mobile applications a query. The category or query associated with the allow users to read neatly presented news stories user is then the simplest form of user profile found from numerous media houses using interfaces that in mobile news apps. For full-fledged require only very limited interaction with the recommender systems, though, a more system. The features of these apps vary, though comprehensive representation of user interests and information filtering and user friendliness are key preferences is needed to provide personalized news features of many of these applications (Haugen, services. If news stories read in the past is a good 2013). indication of the user’s current preferences, we need Advanced recommendation technologies are still to analyze these stories and find ways of capturing rare in commercial news apps, but some of them their content in her user profile. If stories read by now include simplified recommendation features, friends or similar people are assumed to be relevant, and several research prototypes experiment with we need ways of relating the user’s profile to other new and promising recommendation approaches that users’ profiles and find exactly those other users that analyze both the content of news articles and the have read news stories that are most likely to be of users’ social networks. This is not very surprising, interest to her. There are many aspects of user as mobile news may benefit from these profiles, and the choice of recommendation recommendation technologies for a number of technique also influences the structure, content and reasons: (i) the constant flow of news easily leads to maintenance of these profiles. information overload problems for the reader, (ii) The NTNU SmartMedia project is experimenting the small screen prevents the apps from showing with advanced recommendation techniques in a Gulla J., Fidjestøl A., Su X. and Castejon H.. 185 Implicit User Profiling in News Recommender Systems. DOI: 10.5220/0004860801850192 In Proceedings of the 10th International Conference on Web Information Systems and Technologies (WEBIST-2014), pages 185-192 ISBN: 978-989-758-023-9 Copyright c 2014 SCITEPRESS (Science and Technology Publications, Lda.) WEBIST2014-InternationalConferenceonWebInformationSystemsandTechnologies news app for Norwegian newspapers. Users are in been read. Techniques like decision trees, Bayesian this app associated with devices, and the mobile classifiers, support vector machines, singular value news recommender engine ranks news using a decomposition, clustering and various similarity combination of freshness, geographical proximity scores have been used as part of this estimation and match with users’ preferences. Central in the process. work is the definition of user profiles that reflect and In content-based filtering, which is the primary interpret user behavior and support both content- concern of this paper, the estimation is all based on based and collaborative filtering. the content of previously read news articles. The The purpose of this study is to investigate to assumption is that users read articles on topics they what extent a minimalistic swipe-based mobile news find interesting, and the users’ interests do not interface can be used to infer user preferences change substantially from one day to another. If a without any explicit signals from the users. The particular user preferred to read about politics one paper itself is structured as follows: After the day, chances are good that she will also be interested introduction in Section 1, we discuss the particular in political news the next day. Moreover, the degree challenges and needs in news recommender systems of interest in a topic may be reflected in the in Section 2. In Section 3 we briefly present earlier frequency with which the user visits news stories of work on user profiling in recommender systems. this topic or category. Section 4 introduces the SmartMedia news recommendation project and its overall method for 2.1 News Challenges extracting user profiles from end user’s interaction with the mobile app. After discussing the way this Recommender systems for products and services profiling technique can be configured to serve normally deal with items that are rather stable both different purposes in Section 5, we conclude the in terms of number and descriptions. The paper in Section 6. recommendation task is to compare a fixed number of items that all have structured and well understood properties. There is no relevant temporal dimension, 2 NEWS RECOMMENDATION and there is no problem separating one product or service from another. A news recommender system filters incoming news The news domain is intrinsically more dynamic and presents to each individual user a ranked list of and unpredictable to deal with. There are new news that it deems most relevant to the particular stories coming up all the time. Some of these user at hand. Since these are articles that the users uncover new events, while others just report on the have not already read and evaluated, we need to find progress of an already published event. There may a way of guessing users’ interests based on their be several conflicting stories of the same event, but previously observed behavior. there may also be several events discussed in the In formal terms, the task in news same story. recommendation is to estimate and rank the For news recommendation there are three evaluations of news articles unknown to a user particular challenges that need to be addressed: (Borges & Lorena, 2010; Jannach et. al, 2010). First, the news domain is characterized by Assume a set of users U and a set of news articles A, fluctuating and unclear vocabularies and ever the recommender system needs a utility function s changing news topics. Rather than ranking a fixed that defines the evaluation v of an article a for a user number of products, the system need to rank a u: dynamically growing number of events that may have very little in common with what the user read : →, yesterday. The vocabularies change as new stories in which V is a completely ordered set formed by emerge, making it difficult to detect how stories are non-negative values within an internal, e.g. 0 to 1 or related and thereby estimate their relevance to the 0 to 100. The system will recommend an article a’ user. that maximizes the utility function for the user: Second, the short life span of news stories renders most news stories irrelevant, even though argmax, ∈ they seem consistent with the user’s interests. For a For those articles that have not been evaluated by the developing story, it makes sense to recommend the user, the system needs to estimate their evaluations latest article, unless there are substantial differences from relatedness with other articles that have in fact in quality and depth that make an older article more 186 ImplicitUserProfilinginNewsRecommenderSystems informative. On the other hand, if collaborative to require that the user enter and regularly update filtering is used, it may be difficult to pick up the extensive representations of her interests, though, latest article before anyone else in your community and more advanced techniques for profile has read and rated it. construction on the basis of implicit feedback are Third, most media houses consider serendipity to needed. be important to hold on to its readers. Serendipity A system combining explicit feedback and refers to the introduction of news that may not have automatic learning is described in Singh et. al been selected or preferred by the user, but may still (2006). After building an initial interest category be interesting because they are surprising, alarming, hierarchy on the basis of explicit feedback on a important, have a particular journalistic quality, or number of articles, the system analyzes user simply add variation into the news stream. feedback from ongoing news sessions and Serendipitous news help media houses expand users automatically adds new leaf categories or update interests in their products, since they persuade users existing ones in the interest hierarchy.